Desulfurization of hydrocarbons by extraction with phenylacetonitrile



Weightpercent, u I I Patented Jan. 19, 1954,

DESULF'URIZATION OF HYDROCARBONS BY EXTRAGTION WITH PHENYLACETO- NITRILE Nor-wood K. Talbert, Yorklyn, Del., assignor to Phillips Petroleum Company, a corporation of Delaware Application June 8, 1951, Serial No. 2.30.521

16 Claims. (01. 260-608) This invention relates to the separation of sulfur compounds and hydrocarbons from mixtures of them. In one of its aspects the invention relates to the removal of sulfur compounds from hydrocarbons. In another aspect the invention is concerned with the extraction of aliphatic disulfides from hydrocarbons. In still another of its aspects the invention relates to a process for the selectiveextraction of sulfur compounds from paraf fin-ic and naphthenic hydrocarbons containing them, employing an agent novel for this purpose.

It is generally impossilole to separatealiphatic sulfur compounds from'h fractional distillation because. the sulfur compounds have boiling points within the boiling ranges of valuable hydrocarbons-contained in the fraction, and, in some cases at least, azeotropes' are formed.

Methods now employed for separating atl'east a portion of the sulfur'compounds from hydro carbons are solvent extraction and extractive distillation, using polar compounds which are preferential solvents for the sulfur compounds. Most of these solvents are unsatisfactory because they either have low aliphatic disulfide solubility or they are miscible with hydrocarbons; or, at hestrtheyhave limited. selectivity tor alip ati disulfid s.

A tabulation of a number-of; solvents. and the reasons. why each is notisatisfactory for the removal of aliphatic disulfides from hydrocarbons isgiven in Table I. Ditertiaryoctyldisulfide was used as; the representative of aliphatic disulfides, and normal heptane was used. asrthe respxesenf'tative o1: parann'hydrqcarpons; f-addition to the. tabulationfgivenf in'IablefL, I have. obtained data which sh ws the. system. ;benzonitrile=di- -;t.ertiaryeo yldisulfide iwas completely miscible *sbove approximately SMF; 'rorconcentration of disulfide from 31.5 weight per'llgentf'jto 159,7

'drocarbon mixtures by TABLEI Solvents tested for disulfidcwparafiin separation 'Solvent Remarks n-Acetyl ethanolanfine Immiscible with disulfide. o-Anisidinc Low selectivity for disulflde with V respect to par-afiins.

n-Buty'romtnle Completely miscible with both 1 parafflns and aromatics.

n-Capromtnle. i. Completely miscible with both parafiins and disulfides. Di-nprcpylanllme. Do. '2-ethanolpyrld1nc. Immiscible with disulfide. 4*ethanolpyridine. Do. Ethyl cyanoacetate. Do. Ethylene cyanohydrl Do. Ethylene gl oln m Do. Heptacosafluorotrl-n-butyl Do.

amine. B-hydroxyethyl acetate... Do. B-hydroxyethylamlmc.. Do. Levuliuic acid. Do. Methyl acetoacetate. Do. Methyl levulmata.-- :Do. Monoethanolarmne" Do. .o-Nitroanisolc n Low selectivity for disulfidc with 1 i respect to' plaralfips. Propylene glycol .i immiscible w th dlsulfidc.

3t El-hyagent is :employedin a .liquiddiquid extraction process or in an extractive distillation procass I and is phenylacetonitrile. iPhenylace'tonitrile hasa great selectivity for aliphatic disulfidesain the presence of hydrocarbons.

A-schematic flow diagram of a' typicaliliquidliquid extraction process .using phenylacetonitrile is giveninFigure'l. "In-this-process:acd-iw wsulflde para'ifin mixture :is processed to produce 4 1a maraffin hydrocarbon :product which is consentially freeilfrom disulfides. ,Tlie mixture-iis con- 'tacted with the' primarysolve'nt henylacetoni- -carbons saturated with phenylacetonitrile is vent. The extract from unit I, which is phenylacetonitrile containing dissolved disulfide concentrate, is contacted with a secondary solvent, which may be a light alkylate, in unit III. The secondary solvent and disulfide concentrate from unit III are separated in unit IV. Some of the disulfide concentrate from unit IV is returned to unit I as enriching liquid, and the remainder is sent to product storage. The secondary solvent from unit IV along with some make-up solvent is returned to unit III. The primary sol vent from unit III which is saturated with secondary solvent is processed in unit V. The pri- TABLE II Liquid-liquid equilibrium relationships for the system phenylacetonitrile ditertiaryoctyldisulfide-normal heptane TEMPERATURE: 71 F. [Equilibriumconcentrations are given in weight percent] Hydrocarbon-rich phase Solvent-rich phase K m4 ]fide n-Hep- Nisulfide e t nl'mlc Dimo Nisulfide e t mtrlle Di- EC R61 tane trile 01v. Weight m sulfide 7 trile (solv. weight 110 m sulfide 7 K s free) free) 0 93. 6. 5 0 0.070 0 11. 1 88. 9 0 8.00 0.12 7 1. 0 92. 2 6. 8 1.1 073 3.1 11.1 85. 8 21. 8 6. 04 3.1 0.12 26 3. 5 89. 2 7. 3 3. 8 .079 5. 8 11. 1 83.1 34.3 4. 92 1. 7 0.12 14 3 8. 0 84. 1 7. 9 8.7 086 10. 2 11. 1 78. 7 47. 9 3. 69 l. 3 0. 13 12.5 79. 1 8. 4 13. 7 092 14. 1 11.2 74. 7 55. 8 2. 96 1. 1 0. 14 8 Z 18. 2 72. 5 9.3 20. 1 103 20. 0 12.0 68. 0 61. 5 2. 12 l. l 0. 17 7 23. 5 66. 5 l0. 0 26.1 .111 23. 9 12.8 63. 3 65. 1 l. 73 1.0 0.19 5 35.0 51. 1 l3. 9 40. 7 163 35.0 16. 0 49. 0 68. 7 0. 96 1. 0 0. 13 3 K for disulfide. 1 K K for n-heptane. 3 Based on estimated tie lines.

I TABLE III Estimated liquid-liquid equilibrium relationships for the system phenylacetonitrile-ditertiary- 0ctyZdisulfide-cyclohercane TEMPERATURE: 77 F [Equilibrium concentrations are given in weight percent] Hydrocarbon-rich phase Solvent-rich phase K p c 1 fii i i ht nitrile D 1 iifi w m n '1 m 1 ML y 0- e lsu e w su flde hexane Nltnle (solv. w i HO n fide Cy Nimle (solv. w i HQ mixt fid oycu K free) free) K for disulfide Above values are based on estimated tie lines. mary solvent recovered in unit V along with some make-up solvent is returned to unit I, and the recovered secondary solvent is returned to unit III.

The liquid-liquid equilibrium relationships for 'the phenylacetom'trile ditertiaryoctyldisulfidenormal heptane system at 77 F. have been determined, and the compositions of the coexisting equilibrium phases are presented in Table II. Values of relative K are included in this table. The relative K is indicative of the selectivity of a solvent for a given compound in the presence of one or more other compounds. A compound -pounds have boiling points within the boiling ranges of valuable hydrocarbons contained in the fraction.

Detailed information concerning the phenylacetonitrile process for the removal of ditertiaryoctyldisulfide tflomynormal-zheptaneeisjLgiveniin =Fig'urezb2. ';EEhe;.-contactor, unit.I,-.:'i "provided with:trays;V risers; rand iiownecomers in eldel 'ifi) obtain intimate: contacting. of. :the hydrocarbon aphasewith phenylacetonitrile. Any: other suitablegmeans of contacting the hydrocarbon-phase with the solvent could have been used. i'I-he basis oft-he schematic 'flow diagram :(Eigurer 2) .is illiOOpounds fof hydrocarbon feed. "Ihe deedis a. binary mixture; :of normal heptane and =diteritiaryoctyldisulfide :containing 7 l .flvweightper cent disulfide, The disulfide concentrationvpfathe normalzheptane is :reduced; to 0.1 per cent by extraction with phenylacetonitrile. As the disulfide concentrate contains 565: fiweig-ht perlcent disulfide, the normal heptane loss-in this stream is only pounds per 1000 pounds of feed. The ,liquid-jliquid contactor has three theoretical rected to unit II, which is a stripping column,

wherein the normal heptane and phenylacetonitrile are separated. The phenylacetonitrile is returned to unit I, and the normal heptane, which is essentially free of disulfide, is directed to product storage. The extract from the contactor is processed in the hydrocarbon-solvent separation step wherein the operations illustrated by units III, IV and V of Figure 1 are accomplished. The phenylacetonitrile extract from unit I is contacted in unit III with the secondary solvent, which may be a light alkylate with a boiling range of 100 to 300 F. and preferably a narrower boiling range such as 210 to 240 F., or a hexane fraction with a boiling range such as 122 to 156 F. The disulfide concentrate is extracted from the phenylacetonitrile by the light alkylate. The disulfide concentrate and light alkylate are separated in a stripper, unit IV; 297 pounds of disulfide concentrate per thousand pounds of feed are returned to the contactor as enriching liquid, and theremainder, 14 pounds, is sent to product storage; the light alkylate is returned to unit III. The phenylacetonitrile from unit III which is saturated with light alkylate is processed in unit V. In unit V the light alkylate is stripped out of the phenylacetonitrile. The phenylacetonitrile is returned to unit I and the light alkylate is returned to unit III.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, drawings, and appended claims to the invention; the essence of which is that phenylacetonitrile has been found to bean excellent selective solvent agent for the extraction or removal of sulfur compounds from hydrocarbons and that a method for such removal has been set forth as described.

I claim:

1. The removal of a sulfur compound from a hydrocarbon containing it which comprises the step of contacting said hydrocarbon with phenylacetonitrile. I

2. The process of claim 1 wherein a liquid t liquid extraction method is employed.

3. The process of claim 1 wherein an extractive distillation method is employed.

4. The process of claim 1 wherein the temper ature iis maintained in tnerang' SOP-FI to ELO'O F.

5. The removalbf an aliphatic disulfide from a hydrocarbon by contacting said T hydr'ocaibon with .-.phenylacetonitrile, separating a raffinate containing hydrocarbon and f phenylacetonitrile from ea r. phenylacetonitriledisulfide-containing extracpand then recovering said disulfide from said extract.

The removal of a ditertiaryoctyldisulfide from-a hydrocarbon by contacting said hydrocarbon withphenylacetonitrile, separating arraifinate-containing hydrocarbon "andlphenylacetonitrile f rom a phenylacetonitrile-'disultide-contain-ing- 1 extract and then recovering said 'disulfide-rromsai'd extract.

7 ."Iitie remcv' l or a ditertiaryoctyldisulfide from n-hepta'ne' by contacting said n-heptane with phenylacetonitrile, separating a rafiina'te containing n'-heptaiie and phenylacetonitrile from I a phenylacetonitrile-disuIfide-contaifiifi extract. ana' tnea iec'dvenng said disulfide" from said extract.

8. The process for the separation of an aliphatic disulfied from a substantially saturated hydrocarbon containing it which comprises contacting said hydrocarbon with a primary solvent essentially phenylacetonitrile, separating from the contacted admixture, thus obtained, a ramnate containing hydrocarbon and phenylacetonitrile, separating phenylacetonitrile from the rafilnate, separating a hydrocarbon fraction, essentially free irom disulfide, as a product of the process, returning the phenylacetonitrile to the contacting step of the process, separating from the said contacted admixture an extract rich in disulfide, treating said extract with a secondary solvent to extract disulfide therefrom, separating disulfide from said secondary solvent as another product of the process, recovering phenylacetonitrile from said solvent and reusing both the last recovered phenylacetonitrile and secondary solvent in the process as before.

9. The process for the separation of ditertiaryoctyldisulfide from a heptane containing it which comprises contacting said heptane with a primary solvent essentially phenylacetonitrile, separating from the contacted admixture, thus obtained, a raffinate containing heptane and phenylacetonitrile, separating phenylacetonitrile from the raiiinate, separating a heptane fraction, essentially free from disulfide, as a product of the process, returning the phenylacetonitrile to the contacting step of the process, separating from the said contacted admixture an extract rich in disulfide, treating said extract with a secondary solvent to extract disulfide therefrom, separating disulfide from said secondary solvent as another product of the process, recovering phenylacetonitrile from said solvent and reusing both the last recovered phenylacetonitrile and secondary solvent in the process as before.

10. The recovery of ditertiaryoctyldisulfide from normal heptane which comprises contacting the normal heptane containing said disulfide with phenylacetonitrile in the liquid phase, separating saidcontacted admixture into raffinate and extract phases, said raffinate phase containing normal heptane and phenylacetonitrile, separating normal heptane from phenylacetonitrile as a product of the process and returning said separated phenylacetonitrileto the contacting step, contacting the said extract phase containing phenylacetonitrile and disulfide with a light hydrocarbon alkylate boiling in the range of to 300 F. thus separating a disulfide concentrate from the phenylacetonitrile, then separating the disulfide concentrate from the light alkylate and removing disulfide as a product of the process while returning some disulfide as enriching liquid to the contacting step, returning the alkylate to the step in which the extract phase is contacted with light alkylate, and returning the phenylacetonitrile to the first mentioned contacting step.

11. The process of claim 10 wherein the light alkylate has a boiling range of from 210 to 240 F.

12. The process of claim 10 wherein the light alkylate is essentially a hexane fraction boiling within the approximat range 122 to 156 F.

18. The process of claim 10 wherein the temperature during the contact of the phenylacetonitrile and the heptane is maintained at approximately 7 7 F.

14. The removal of sulfur compounds from a saturated hydrocarbon with phenylacetonitrile which comprises contacting said saturated hydrocarbon with phenylacetonitrile to obtain an extract phase and a raffinate phase, separating a ratfinate containing said hydrocarbon and phenylacetonitrile from a phenylacetonitrile-su1fur compound containing extract and then recovering said sulfur compound from said extract.

15. A process according to claim 14 wherein. said saturated hydrocarbon is an aliphatic hydro-- References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,069,329 Roelfsema Feb. 2, 1937 2,114,852 McKittrick Apr. 19, 1938 2,162,963 McKittrick June 20, 1939 

1. THE REMOVAL OF A SULFUR COMPOUND FROM A HYDROCARBON CONTAINING IT WHICH COMPRISES THE STEP OF CONTACTING SAID HYDROCARBON WITH PHENYLACETONITRILE. 